LED Light Painting

There are quite a few LED strip based matrix displays out there that imitate a low resolution television screen. What I wanted was an LED matrix that has a lot of light diffusion so it is perfect for abstract displays. Light diffusion can be achieved in many ways, I chose a light cotton painters canvas for this, but a white acrylic sheet would work as well. Combine the hardware with the WLED software by Aircoookie, and it makes for a beautiful, adaptable piece of light art. Colors and patterns can be selected using the WLED app on your phone.

The diffusion works best when the canvas is about 3 centimeters away from the LEDs. A canvas is usually not as thick as that, so we need to raise it using a wooden slat. We only need to raise the sides, as the light shining through the top and bottom opening adds a surround, "ambilight" style of effect. To make this effect even beter two LED strips are added to the back, mounted on angled wood trim pieces.

The LED matrix is created by sticking the self-adhesive LED strips to the board at the same distance as the LEDs have between the strips. This creates an even pattern of light, where the light of each LED blends over into the next one.

Dimensions for one 60x90 canvas, adapt as needed:

• The canvas has a frame 5 cm wide, so 50x80 cm is left for the LEDs
• Length of each strip is 23 LEDs x 3.33 = 76.6 cm
• 14 LED strips to form the matrix at 3.3 cm apart = 46.6 cm
• 2 strips on the back for "ambilight" effect
• Total number of LEDs: 16x23=368 LEDs
• Power consumption can be 60mA per LED, so 22A total.
• As this is quite a lot of power and we're using thin wire we'll need to insert power into the strips at each alternating strip. The thin massive copper wire makes soldering to the LED strips a lot easier though.

Hardware:

• 90x60 plywood base
• 90x60 cotton painters canvas (5cm wide frame)
• 2x 90x5x2 wood slats for raising the canvas to at least 3 cm from the LED strips
• 2x 80 cm angled wood trim for "ambilight" effect
• wood glue, screws

Electronics:

• Wemos D1 mini ESP8266 module: https://wiki.wemos.cc/products:d1:d1_mini
• 5V logic level shifter: https://www.aliexpress.com/item/32624528143.html?spm=a2g0s.9042311.0.0.27424c4d1LhNvr
• LED strips: 3x SK6812 RGBWW 5 meter reels non-waterproof with 30 LEDs per meter
• Power Supply: at least 22A at 5V
• 8x Excellway 5 pin spring terminal block
• 5 meters massive copper core 22 gauge (telephone) wire to LED strips
• regular 110V/220V wiring for power and cable with appropriate power plug
• WLED software: https://github.com/Aircoookie/WLED

We start this project by configuring the Wemos ESP8266 module. You'll need a micro USB cable to connect it to your computer. You can then flash the Wemos Module by downloading a pre-compiled binary from the wled site: https://github.com/Aircoookie/WLED/releases and flashing it using the esphome flasher program from this site: https://github.com/esphome/esphome-flasher/releases

Once flashed you can login to the Wifi access point that is running on the module, and change the wifi to your own network. After you find out the WLED's IP address from your router, you can configure the WLED software by using the WLED app on your phone:

• Set the number of LEDs to 368
• set the maximum current to 65000
• Mark the box for RGBW
• Set the Color Order to GRB

Cut the 5m LED strips into 16 sections of 23 LEDs. You will have three strips of 12 left over for other projects.

Solder seven sets of two LED strips together with three wires on one end like so. Watch the directional arrows on the strip!

Combine the seven sets with data and solder 30 cm long wires for power and ground to each set: (three sets shown, imagine there are seven)

Glue/Screw the wood spacer slats to the left and right of the front of the plywood board. These spacers should provide a distance between the LEDs and the canvas of 3 cm.

Mark out the locations on the plywood board and stick the strips to the board. the LEDs should form an even pattern with 3.3 cm of distance measured from left edge to the left edge of the strips. Leave an even space to the left and right of the matrix to the spacer slats.

Drill holes into the plywood just below the strips to let the power wiring and data lines through. The start of the matrix is at the bottom right corner when seen from the front, so left bottom corner as seen from the back.

Glue/Attach the angled wood trim pieces to the back of the board at about 10 cm from the edges, and stick the "ambilight" strips to them. Mind the direction of the strips!

Solder the blue data line to the "ambilight" strips and to the logic level shifter and Wemos. Solder 30cm wires for ground and power to the rear LED strips, logic level and Wemos module.

Use the Excellway connectors to make a power and ground distribution from the 5V power supply to the LED strips, Wemos and logic level shifter. Use thicker wire to go from the 5V power supply to the Excellway, and connect to the components using thin wire.

Attach the 5V power supply to the rear of the board and connect a power cord. Make sure there is strain relief on the mains power cable using trie wraps or something similar. A bit of extra length on the power cord is a good idea.

Power on the system and test it out. Once all leds are found to be OK, attach the canvas to the front using screws (from the back). I had to saw off a wood support slat in middle of the canvas frame that was blocking the light.You may also want to add some trim pieces to the side of the painting to finish it off.

Now mount it on a wall using some sturdy wire and enjoy the light show!